State officials say farmers should avoid spreading manure this month on fields that are prone to runoff.
The state Department of Natural Resources says melting snow and rain can carry the manure into lakes, streams and groundwater, presenting a risk both to animals and humans.
The DNR says farmers should stack manure away from fields near lakes or rivers, as well as from drinking water wells and areas with sinkholes or exposed bedrock.
Officials say farmers who have to spread should carefully do so at less risky fields and have plans to deal with spills.
The department has an online advisory system that predicts runoff risks and keeps farmers updated with field conditions three times a day.